Quantitative analysis of glucosinolates by LC-MS

The LC–MS analysis was performed using an Advance UHPLC system (Bruker, Bremen, Germany) with a Kinetex XB-C18 column (100 × 2.1 mm, 1.7 μm, Phenomenex, Palo Alto, U.S.A.) coupled to an EVOQ Elite TripleQuad mass spectrometer equipped with an electrospray ionisation source (ESI) (Bruker, Bremen, Germany). The method was performed as previously described [46 ,47 (link)] using formic acid (0.05%) in water and formic acid (0.05%) in acetonitrile as mobile phase A and B, respectively. Ionisation was obtained by electrospray ionisation in positive ionisation mode with spray voltage of 3500 V and probe and cone temperatures at 400 and 350°C, respectively. Parent ion to product ion transitions were monitored for one aromatic (2-phenylethyl), three indolic (indol-3-ylmethyl, N-methoxy-indol-3-ylmethyl, 4-methoxy-indol-3-ylmethyl) and nine aliphatic (3-methylthiopropyl, 3-methylsulfinylpropyl, 4-methylthiobutyl, 4-methylsulfinylbutyl, 5-methylsulfinylpentyl, 7-methylthioheptyl, 7-methylsulfinylheptyl, 8-methylthiooctyl, 8-methylsulfinyloctyl) glucosinolates. Quantification of individual glucosinolates was done using p-hydroxybenzyl glucosinolate as internal reference. Further details and transitions can be found in [46 ,47 (link)].